Convert Teaspoons to Milliliters

One Teaspoon = 4.929 mL

The US teaspoon is exactly 4.92892159375 mL, which everyone rounds to 5 mL. That 1.4% difference between the legal US teaspoon and the 5 mL metric standard is irrelevant for cooking. It is not irrelevant for medication, where a 1.4% difference compounded over multiple doses per day can add up.

Unlike tablespoons, teaspoon sizes are fairly consistent worldwide. The US, UK, Canada, and Australia all use approximately 5 mL as a teaspoon, give or take fractions of a milliliter. The Australian tablespoon is the famously different one, not the teaspoon.

Medicine Dosing: The Real Reason This Gets Searched

Children's liquid medications (ibuprofen, acetaminophen, cough syrup, antibiotics) are prescribed in milliliters. Parents reach for the teaspoon in the kitchen drawer. This is a dosing error waiting to happen.

Actual tableware teaspoons range from about 2.5 to 7.5 mL, according to a study published in the Annals of Internal Medicine. That variability means you could be giving half or double the intended dose by using a random spoon from your drawer. Use the milliliter-marked syringe or cup that comes with the medication.

Baking Precision at Small Volumes

Teaspoons are the standard measure for leavening agents (baking powder, baking soda), salt, vanilla extract, and spices. These are the ingredients where small differences matter most. Half a teaspoon of baking soda (2.5 mL) versus a full teaspoon (5 mL) can be the difference between a cake that rises properly and one that tastes metallic.

The relationships to remember:

• 3 teaspoons = 1 tablespoon
• 48 teaspoons = 1 cup
• 1 teaspoon is about 5 mL

How to Measure a Half Teaspoon Without a Half-Teaspoon Measure

If you only have a 1-teaspoon and a 1-tablespoon measure, you can still measure any fraction. Fill the teaspoon halfway by eye for 0.5 tsp (2.5 mL). For 0.25 tsp (1.2 mL), fill it a quarter of the way. This seems imprecise, but experienced bakers do it routinely and get consistent results. The visual trick: a half teaspoon fills the spoon to about the level where the bowl starts to flatten, not to the midpoint of the total depth.

For anything more precise than quarter teaspoons, switch to a scale. A quarter teaspoon of salt is about 1.5 grams, which a decent kitchen scale can read.